Dissolving soluble thermoplastic resins in reactive diluents and then mixing these into vinyl functional resins to reduce shrinkage is known in the art. This process however does not produce interpenetrating polymer network compositions and/or pseudo interpenetrating network polymer compositions it is simply a mixture as evidenced by the physical properties of resultant cured mass. Simply mixing two or more polymers does not create an interpenetrating polymer network (polymer blend), nor does creating a polymer network out of two or more monomers that are bonded to each other to form one polymer molecule (heteropolymer or copolymer).
For example, in making fibre glass, thermoset IPN composites, if the amount of glass required can be reduced or in certain application no glass is required then much tougher resin systems can be formulated This is because thermoset IPNs have superior elongation and much lower shrinkage than the thermosets from which they are formulated. The presence of short glass fibres in Very Short Fiber Polymerizable Liquid Composites (VSFPLC's) is useful to prevent (or reduce) crack formation during the curing process when injection moulding parts when using commercially available thermoset resins as the matrix resin. The presence of these fibres increases yield stress and modulus but reduces the elongation of the cured composite. The decrease in elongation in certain applications equates to an increase in brittleness. Glass is also used in composites to reinforce the resin during gelation and to reduce shrinkage. The presence of glass fibres is therefore typically used in vinyl functional liquid thermosets. If there was minimal shrinkage during gelation and final curing of the resin then glass fibres would not be required or may be reduced to produce serviceable moulded parts. The reduction in shrinkage and increase in elongation allows SIPN and/or IPN resins to be moulded without the need for glass reinforcement.
Disclosed in the art are composites produced with VSFPLC resin compositions. However, certain of these compositions lack sufficient toughness (as measured by the area under the stress strain curve) for certain applications. Fabricators have a need for tougher products.
One factor that influences toughness is elongation. There are resins on the market which have adequate elongation and yield stress. These resins however tend to have low heat distortion temperatures (HDT). For exterior applications it is expected that the HDT of a cured resin should be at least 80 C.
This has been achieved with certain rubber modified vinyl ester (VE) resins, but these are relatively expensive and they have limitations. For example, rubber modified VE resins may have one or more of the following issues: they stick in moulds, are expensive, shrink when cured, their HDT is limited to about 80° C. and they have minimal acceptable elongations, all of which limits their wider market acceptance.
One of the other problems with vinyl functional thermosets is that they polymerize into vitreous solids and are inherently brittle. There is a practical limit to the distance apart of the vinyl groups in the unsaturated polyester (UP) or VE molecule. This is one of the reasons why the higher the elongation (i.e. the greater the distance apart of the vinyl groups) the lower the HDT. This is caused by the lower crosslinking density and is a direct consequence of increasing the intramolecular distance between the crosslinking sites. There is a need for new vinyl functional resins in order to improve the performance of VSFPLC's and to provide commercially feasible tough serviceable resins. Certain methods and/or systems disclosed herein provide IPNs and/or SIPNs that provide commercially feasible tough serviceable resins.
The combination of polyurethane and vinyl functional resins to form various resins is known in the art. These processes involve growing the polyurethane through the vinyl functional thermoset using a chemical process, which is a chemical approach as compared with the physical processes disclosed herein. These types of resin compositions require careful storage conditions to prevent premature polymerization. Also, the required resin injection equipment involves an extra injection pump, which makes the system more difficult to use. They are not widely used because of the difficulty in controlling these systems. In addition, these systems have a high shrinkage factor which makes them more difficult to mould parts with.
Accordingly, systems, methods, resin compositions, and/or resin composites that ameliorate these and other problems disclosed in the art are desirable. The present disclosure is directed to overcome and/or ameliorate at least one of the disadvantages of the prior art, as will become apparent from the discussion herein. The present disclosure is also to provide other advantages and/or improvements as discussed herein.